ISR(TIMER1_CAPT_vect){

  if(isrbusy)uart_sendl("ISR collision"); // We never see this
  isrbusy = true;

  // Flip looking for rising or falling edges
  // FIXME: This can be greatly abbreviated

  if(TCCR1B & (1<<ICES1)){
    TCCR1B &= ~(1<<ICES1);
  } else {
    TCCR1B |= (1<<ICES1);
  }

  // Figure out time since last edge

  uint16_t this_edge_duration;

  if(ICR1 > ltc_last_edge_time){
    this_edge_duration = ICR1 - ltc_last_edge_time;
  } else {
    ltc_timer_overflows++;
    this_edge_duration = ICR1 + (0xFFFFUL - ltc_last_edge_time);
  }

  // Record the time of this edge

  ltc_last_edge_time = ICR1;

  // Figure out whether this was a long or short bitperiod
  // and if it was short, figure out if it's the second short
  // one in a row. Push the result to the buffer.

  if(this_edge_duration>ltc_bitperiod_threshold){
    // It's a zero. Zero the last bit in the buffer.
    wptr[9] &= ~(0x80);
    if(ltc_short_wait_flag==true){
      // This really never fires, other than maybe once
      ltc_short_wait_flag = false;
    }
  } else {
    // It's possibly part of a 1
    if(ltc_short_wait_flag){
      // It's a one. Set the last bit in the buffer.
      wptr[9] |= 0x80;
      ltc_short_wait_flag = false;
    } else {
      // It's presmably the beginning of a one
      ltc_short_wait_flag = true;
      isrbusy = false;
      return;
    }
  }

  // Check to see if we've found a full frame

  if(wptr[8] == ltc_magic_number_A_rev && wptr[9] == ltc_magic_number_B_rev){

    // Calculate the precision frame duration

    ltc_frametime = 0xFFFFUL - ltc_frame_start_time;
    ltc_frametime += 0xFFFFUL * (ltc_timer_overflows-1);
    ltc_frametime += ICR1;

    uart_sendl(ltc_frametime);
    glitches = 0;
    ltc_frametime = 0;
    ltc_frame_start_time = ICR1;
    ltc_timer_overflows = 0;
    //ltc_decode_frame();

    // Swap buffers

    if (rptr == ltc_buf){
      rptr = ltc_buf2;
      wptr = ltc_buf;
    } else {
      rptr = ltc_buf;
      wptr = ltc_buf2;
    }

  }

  // Shuffle the buffer

  for(uint8_t i = 0; i < 10; i++){ // Remember we made an extra byte on the end we don't need?
    wptr[i] = (wptr[i] >> 1) | (wptr[i+1] << 7);
  }
  isrbusy= false;
}